Compositions and methods for the prevention of asthmatic symptoms

ABSTRACT

There are disclosed compositions containing a number of benzodipyrons, e.g. 4,10-dioxo-2,8-dicarboxy-5-methoxy-4H,10Hbenzo(1,2-b:3,4-b&#39;&#39;) dipyran, and the use of these benzodipyrones in the treatment of conditions in which antigen reactions are responsible for the conditions.

United States Patent [191 Cairns et al.

[ Feb. 4, 1975 COMPOSITIONS AND METHODS FOR THE PREVENTION OF ASTHMATIC SYMPTOMS [75] Inventors: Hugh Cairns, Sandbach; Robert Minshull, Brereton, both of England [73] Assignee: Fisons Limited, Felixstowe, Suffolk,

England [22] Filed: Dec. 8, 1972 21 App]. No.: 313,266

Related U.S. Application Data [60] Division of Ser. No. 62,170, Aug. 7, 1970, Pat. No. 3,718,668, Continuation-impart of Ser. No. 751,753, Aug. 12, 1970, abandoned.

[30] Foreign Application Priority Data Aug. 17,1967 Great Britain 37912/67 Apr. 2, 1970 Great Britain 15577/70 [52] U.S. Cl 424/283, 424/263, 424/274 [51] Int. Cl A6lk 27/00 [58] Field of Search 424/263, 274, 283

Primary ExaminerStanley J. Friedman Assistant Examiner-Norman A. Drezin Attorney, Agent, or F [rm-Wenderoth, Lind & Ponack [57] ABSTRACT There are disclosed compositions containing a number of benzodipyrons, e.g. 4,10-dioxo-2,8-dicarboxy-S- methoxy-4H,l0H-benzo(1,2-b:3,4-b') dipyran, and

the use of these benzodipyrones in the treatment of conditions in which antigen reactions are responsible for the conditions.

12 Claims, No Drawings COMPOSITIONS AND METHODS FOR THE PREVENTION OF ASTHMATIC SYMPTOMS This is a divisional application of Applicants copending application Ser. No. 62,170 now, US. Pat. No. 3,718,668, which in turn is a continuation-in-part application of application Ser No. 751,753 filed Aug. 1 1 9a owsa a td9nsd The present invention relates to novel compounds, their preparation and use,

' According to the invention there are provided, as new compounds, benzodipyrones of the formula I,

COH

in which one or more adjacent pairs of P, Q, R and T, together form the chain -COCR =C(COOH)--O which may be bonded to the benzene ring in either sense; the remainder of P, Q, R and T are the same or different and each is hydrogen; alkyl containing from 1 to carbon atoms (e.g. methyl, ethyl, butyl, pentyl, and hexyl groups); alkyl containing from 1 to 10 carbon atoms and carrying a halo; hydroxy; lower alkoxy, e.g. methoxy, ethoxy, propoxy or pentoxy; acetoxy; carboxy; amino; lower alkaylamino e.g. ethylamino, butylamino or pentylamino; lower di-alkylamino; e.g. dimethylamino, diethylamino, dibutylamino, dlpentylamino; or a hydroxylamino substituent group;

unsaturated alkyl containing from 1 to 10 carbon atoms (e.g. alkenyl .such as ally] and propargyl); phenylalkyl (e.g. benzyl and phenethyl groups), halophenylalkyl or alkylphenylalkyl wherein the alkyl groups contain from 1 to 10 carbon atoms; phenyl; naphthyl; or phenyl and naphthyl carrying a halo, lower alkyl, nitro, carboxy or hydroxy substituent group;

pyridyl; furyl; pyrrolyl; cycloalkyl containing from 4-6 carbon carbon atoms (e.g. cyclopentyl or cyclohexyl); cycloalkyl containing from 4-6 carbon atoms and carrying a 1 hydroxyl, lower alkoxy or carboxy substituent group nitrile; nitro; nitroso; hydroxy; alkoxy containing 1 to 10 carbon atoms cg. methoxy, ethoxy or propoxy; alkoxy containing from 1 to 10 carbon atoms and carrying hydroxy, lower alkoxy, carboxy halo, amino, lower alkylamino, or lower dialkylamino substituent group;

alkenyloxy or alkynyloxy containing from 1 to 10 carbon atoms; benzyloxy; phenyloxy; naphthyloxy; pyridyloxy; cyclohexyloxy; cyclopentyloxy; epoxyloweralkoxy; amino; lower alkylamino e.g. ethylamino and propylamino; lower dialkylamino e.g, dimethylamino and diethylamino; cycloalkylamino containing from 4 to 6 carbon atoms; phenylamino; naphthylamino; diphenylamino; haloloweralkylamino; lower alkenylamino; aminoloweralkylamino, hydroxylamino; lower acyl amino; ureyl; thioureyl; guanidino; thiol; lower alkyl thiol; phenyl thiol; sulphonic acid; halogen e.g. chlorine, bromine, or iodine, or

one or more of P, Q, R and T may be a group OY wherein Y is an alkyl group having from 1 to 10 carbon atoms substituted by lower alkyl or phenyl-lower alkyl in which one or more of the CH groups has been replaced by oxygen, sulphur or carbonyl, which alkyl or phenyl-lower alkyl may carry one or more hydroxyl or carboxyl substituent groups; or an adjacent pair of P, Q. R and T (together with the adjacent carbon atoms in the benzene ring) together from a benzene ring, or

(CH3)O -OCH2O NH-C(R*R CH QrQLRFQHiQHrD+ Q V TQH=.,CH- (wherein R is hydrogen or lower alkyl or lower alkoxy and R is hydrogen, or R and R together form a =0 group),

and each R, may be the same or different and is hydrogen, alkyl containing from 1-10 carbon atoms, alkoxy containing from 1-10 carbon atoms or phenyl and pharmaceutically acceptable derivatives thereof.

It will be appreciated that the chain -CO-CR,=C- (COOH)O may be bonded to the benzene ring in either sense to form the rings R o coca and reference to one chain or ring is intended herein and in the claims to denote bonding in both senses,

Preferred compounds of the invention include those wherein those of P, Q, R and T not forming a CO-CR,=C(COOH)O- chain are hydrogen or halogen, hydroxy, nitro, lower alkyl, lower alkenyl, benzyl, phenyl, lower alkoxy, lower alkenyloxy, phenyl, benzyloxy or the fused ring substituents specified above; and such groups carrying a halogen, hydroxy or lower alkoxy substituent. Particularly preferred compounds are those carrying hydrogen or a halogen (especially chlorine or bromine), nitro or lower alkyl or alkoxy group containing from 1 to 6 carbon atoms which may carry a hydroxy, lower alkoxy or phenyl substituent.

Also preferred are compounds of the formula:

kyl, lower alkoxy, or a lower alkyl or alkoxy group carrying a hydroxy, lower alkoxy or phenyl substituent.

As a further feature of our invention we provide compounds of formula I in which those of P, Q, R and T which do not form a chain COCR,=C(COOH)O- are selected from the group consisting of hydrogen. hydroxy, nitro, halogen, lower alkyl, lower alkoxy or lower alkenyloxy groups (which groups may carry a hydroxy or lower alkoxy substituent), a benzyl group or an adjacent pair of P, Q, R and T may, together with the carbon atoms on the benzene ring form'a fused oxygen containing 5 membered ring, and

each R, is selected from the group consisting of hydrogen, alkyl containing from 1 to carbon atoms. alkoxy containing from 1 to 10 carbon atoms and phenyl.

As a yet further feature of our invention we provide compounds of formula I in which R, is hydrogen and those of P, Q, R and T which do not form a COCR =C(COOH)-O-- chain are selected from methoxy, hydroxy, nitro, methyl, bromo, benzyloxy, ethyl, chloro, allyloxy, butyl, propyl and pentyl.

It will be appreciated that certain of the above values of the P, Q, R, T, P', Q, R and T' include groups which might be detrimentally affected by the reactants and/or reaction conditions used to introduce other groups or the desired cooa rings into the molecule. In such cases the affected group or site may be blocked or shielded, for example by alkylation, acetylation or by the blocking of the reactive site with a removable group such as a cyano or nitro group. 7

Each R may be the same or different and have the values specified above, particularly hydrogen, lower alkyl. eg. methyl, ethyl, propyl, or pentyl; lower alkoxy corresponding to such alkyl groups; or a phenyl group. It is usually preferred that each R group be the same. and further, that each is hydrogen.

Pharmaceutically acceptable derivatives of the compound according to the invention include pharmaceutically acceptable salts, notably water-soluble salts, esters and amides of one or more of the earboxylic acid functions present and esters of any hydroxylic functions present.

Salts of the compounds which may be mentioned are salts with physiologically acceptable cations, for-example, ammonium salts; metal salts, such as alkali metal salts (e.g. sodium, potassium and lithium salts) and alkaline earth metal salts (e.g. magnesium and calcium salts); and salts with organic bases, e.g. amine salts such as piperidine, triethanolamine and diethylaminoethylaventional techniques. Thus, salts may be prepared by the use of alkaline conditions during the recovery and purification 'of the compound. Alternatively, the free acid may be obtained and subsequently converted to a desired salt by neutralisation with an appropriate base, e.g. an organic amine. or alkali such as an alkali metal (e.g. sodium or potassium) or alkaline earth metal (e.g. calcium or magnesium) hydroxide. carbonate or bicarbonate, preferably a mild base or alkali such as sodium carbonate or bicarbonate. Where the compound is recovered in the form of a salt this salt may be converted to a more desirable salt, for example by a metathetical process. The esters may be obtained as a result of hav-v ing used appropriate starting materials. for example by the reaction ofa dialkyl oxalate with an acylbenzene of formula V as hereinafter described; or may be formed by the reaction of an appropriate alcohol, alkyl sulphate or halo-compound with free carboxyl groups in the compound. Alternatively transesterification techniques may be used to exchange one ester group for another. The amides may be readily obtained, for example, by dehydration of the ammonium salt or by reaction of the carboxy ester groups in the compound with an appropriate amino compound such as a primary or secondary amine or an amino acid.

The new compounds of the invention have been shown to inhibit the release and/or action of toxic products which arise from the combination of certain types of antibody and specific antigen, eg the combination of reaginic antibody with specific antigen. In man, it has been found that both subjective and objective changes which result from the inhalation of specific antigen by sensitised subjects are markedly inhibited by prior administration of the new compounds. Thus, the new compounds are of great value in the treatment of extrinsic allergic asthma. It has also been found that the new compounds are of value in the treatment of socalled intrinsic asthma (in which no sensitivity to extrinsic antigen can be demonstrated). In in vitro tests, the compounds have been shown to reduce the release of pharmacologically active substances from passively sensitised human lung tissue after exposure to specific antigen using a modification of the in vitro technique of Mongar and Schild (J. L. Mongar and H. O. Schild, J. Physiol, Vol. lSO (I960). pp. 546-564). The new compounds may also he of value in the treatment of other conditions in which antigen reactions are responsible' for disease, for example, hay fever, urticaria and auto-immunediseases.

According to a further feature of the invention, therefore, there is provided a pharmaceutical composition comprising a compound of general formula I, or a pharmaceutically acceptable derivative thereof, preferably in the form ofa salt, in association with a pharmaceutically acceptable carrier or diluent. There is also provided a process for the manufacture of such a pharmaceutical composition which comprises mixing a compound of the invention with a carrier or diluent.

The nature of the composition and the pharmaceutically acceptable carrier or diluent will, of course, depend upon the desired mode of administration, which may be for example oesophagally; by inhalation; parenlutions or suspensions, as powders or in tablet, cream, lotion or syrup form.

The compounds of the invention find especial use when inhaled by the user, notably in the treatment of allergic asthma. For such use, the compounds ofthe invention, preferably in the form of a salt such as the sodium salt, are dissolved or suspended in water and may be applied by means of a conventional nebuliser. However, the administration of medicaments by means of a pressurised dispensing container. i.e. an aerosol dispenser, is an alternative to nebuliser administration. For administration from an aerosol dispenser, the medicament is dissolved or suspended in the liquefied propellant medium. Where the medicament is not soluble in the propellant, it may be necessary to add a surfaceactive agent to the composition in order to suspend the medicament in the propellant medium, and such surface-active agents may be any of those commonly used for this purpose, such as non-ionic surface-active agents. However, we prefer to use the anionic dialkyl sulphosuccinate or alkyl benzene sulphonate surfaceactive agents. The use ofsu'ch surface-active agents and the advantages which stem therefrom are more fully described in British Patent Specification No.- 1,063,512.

The compositions ofthe invention may also be administered in the form of powders by means of an insufflator device, such as that described in our French Patent Specification No. l,47l,722. In order to improve the properties of the powder, it may be desired to modify the surface characteristics of the powder particles, for example by coating them with a pharmaceutically acceptable material such as sodium stearate. In addition, the fine particle sized powders may be mixed with a coarser diluent material such as lactose.

Whilst the inhalation of medicament has been described above with particular reference to oral administration, it will be appreciated that it may be desirable to administer the medicament nasally. The term inhalation is therefore used herein and in the claims to denote, where the context permits, both oral and nasal administration.

The composition ofthe invention may also be administered as tablets, syrups and the like or by intradermal or intravenous injection in the conventional manner.

In addition to the internal administration, the compounds of the invention may find use in compositions for topical application, e.g. as creams, lotions or pastes for use in dermatological treatments.

In addition to the compound ofthe invention and the ingredients required to present the compound in a form suitable for the selected mode of administration, we have found that other active ingredients may be present in the composition of the invention. Thus, in compositions for administration by inhalation, we have found that it is beneficial to include a bronchodilator. Any bronchodilator may, within reason, be used. Suitable bronchodilators include isoprenaline, adrenaline, orciprenaline, isoetharine and derivatives thereof, particularly the salts thereof. The use of isoprenaline sulphate is preferred. The amount of bronchodilator used will vary over a broad range, depending, inter alia, upon the nature and activity of the bronchodilator and the compound of the invention used. However, the use of a minor proportion (i.e. less than 50% by weight) of the bronchodilator is preferred. We have found that the use offrom 0.1 to 10% by weight of the bronchodilator based on the weight of the compound of the invention is satisfactory.

From a further aspect, the invention therefore provides a composition which comprises a compound of the formula I or a pharmaceutically acceptable derivative thereof in admixture with a bronchodilator, which latter is preferably present in less than 50%, especially 0.] to 10%, by weight of the former.

As indicated above, the compounds of the invention may be used to inhibit the effects of anitbody-antigen reactions and are of especial use in the prophylactic treatment of allergic airway diseases. In such treatments the compound or composition of the invention is administered by the chosen method to the site of the antibody-antigen reaction in the therapeutically effective'amount. The treatment may be one which requires repeated dosages of the medicament at regular intervals. The amount and frequency of medicament administered will depend upon many factors and no concise dosage rate or regimen can be generally stated. However, as a guide we have found that, where the compounds are administered by inhalation to a patient suffering from acute allergic asthma, therapeutically useful results are achieved when the compounds are administered at a dosage rate of from 0.] to 50 mgs. Where the compounds are administered by the oesophagal route, larger dosages may be given.

The invention thus also provides a method for inhibiting the effects of an antibody-antigen reaction which comprises the prior application to the known or expected area ofthe antibody-antigen reaction of a therapeutically effective amount of a compound of formula I or of a pharmaceutically acceptable derivative thereof.

The compounds of the invention may be prepared from compounds of the formula wherein A, and A together form the chain COCR =C(COOH)O-, a chain convertible thereto such as a -CO--CR =C(D)O- or COCH- R CH( D)O- chain (wherein D is a COOR group or a group convertible thereto and R is hydrogen or an alkyl group containing from I to 10 carbon atoms), are groups convertible to the desired chain or to a chain convertible thereto, or are derivatives or precursors of such groups or chains; one or more adjacent pairs of the .groups B B B and B are the groups A. and A the pairs of groups A and A may have the same or different values except that all pairs ofgroups cannot form -CO-CR =C(COOH)O chains; and the remainder of the groups B B B and B, are hydrogen or appropriate substituents.

It will be appreciated that the compounds of the invention possess at least two rings and that these may be the same. Each of these rings may be introduced in separate stages by different or similar methods or may be introduced together in a single reaction stage. It is also possible to introduce in separate stages precursors of one of the desired rings,,

- COQl-l ring. The other ring may be present initially, be formed during the formation of the first ring, or be introduced later by the same or a different process. Where both rings are to be introduced one after another it may be necessary to shield or block the sites at which the second ring is to be introduced. Such shielding or blocking may be achieved by conventional methods as indicated above. The general formula for the starting material,

is therefore to be construed as covering compounds which may be converted to those containing the desired COCR,=C(COOH )-O chain by the same or different methods. It is however preferred that the pairs of groups A, and A have the same values and that each pair is converted to the desired chain by the same.

method in the same reaction process.

The conversion of the A, and A group in the compound may be achieved by a variety of methods. For example the desired ring may be'formed by cyclising compounds ofthe general formulae:

3 COCHCOCOR II B 0M wherein R" is an OH group or a group convertible thereto and-M is hydrogen, an alkali-metal cation or an alkyl group;

cooa 2 III V a n R1 and B3 0 c coon B i 1 B2 4 com cs-0on 1v 1 1 B3 OM' wherein M is hydrogen or an alkali-metal cation, with oxidation or dehydrogenation of the product if required. The desired ring may also be formed by modification of an already formed chromone or chromanone ring [i.e. compounds wherein A and A together form the chain CO--CR,=C(D)-O or CO-CHR,-CH(- D)-O], for example by oxidation of substitue nts in the 2-position of the ring, by dehydrogenation or by intra molecular rearrangement (for example by a Wesseley-Moser rearrangement) The compounds of formula ll may be readily cyclised, for example by heating under non-basic conditions. it is preferred to carry out the cyclisation reaction in a non-reactive solvent such as ethanol or dioxan. It is also preferred to carry out cyclisation in the presence of a cyclisation catalyst, ideally an acid cyclisation catalyst such as a polyphosphoric acid, sulphuric acid, hydrochloric acid, acetic acid or mixtures thereof. When a compound is used wherein M is an alkyl group, simultaneous cyclisation and dealkylation may be achieved by the use of hydroiodic or hydrobromic acid as the cyclisation catalyst.

Cyclisation may be carried out at from ambient temperature to about C, for example by heating the reaction mixture on a steam bath and, where the nature of the reaction medium permits it, under atmospheric reflux.

As indicated earlier, the group R in the compound of formula ll is an OH group, or a group which is convertible to an OH group. Such conversion may have already occurred in the cyclisation of the compound or may have taken place prior to cyclisation. However, where this is not the case, such conversion may be readily achieved using conventional methods. Thus, amino or halogen groups may be hydrolised with a mild alkali, such as sodium carbonate, or an acid.

Alternatively, the R" group may be converted into a more desirable derivative, for example an alkoxy group, and such further conversion is also within the scope of this invention.

The compounds of formula I] may themselves be prepared by a number of methods. For example, an acylbenzene of the formula:

(wherein R, has the value given above and H is.hydrogen, an alkali metal cation or an alkyl group, such as a lower alkyl group, e.g. a methyl, ethyl, propyl or pentyl group), may be condensed with a compound of the for mula R CZCZR, where R, and R, may be the same or different, one being a group reactive with an hydrogen in the COCH R group of the acylbenzene, the other being an R group, and each Z is a carbonyl oxygen or one is an (Hal) group where Hal is halogen. Suitable groups which react with -COCH R group include alkoxyl, amino, alkyl amino, substituted amino or substituted alkyl amino groups. It will be appreciated that these groups include groups which are also convertible to OH groups. Where R and/or R, is an amino or substituted amino group, the nitrogen atom may carry groups E and F where E and/or F is hydrogen, a lower alkyl, a substituted or unsubstituted aryl, alkaryl or haloaryl group. In the case where the nitrogen carries only one group E or F, the substituent may be linked to the nitrogen through a sulphur atom or an -SO- or SO group. Examples of suitable compounds for present use include those of the general formulae R OOC-COR (wherein each R is an alkyl group, such as methyl, ethyl, propyl, butyl group, or pentyl group; an alkaryl group such as a benzyl group; or an alkenyl group such as an ally] group), and R O-C(Hal) COOR (wherein Hal is halogen, preferably chlorine or bromine). Preferred compounds of formula R CZ-CZR for present include diethyloxalate, ethyl ethoxydichloracetate, ethyl oxamate, ethyl oxalylanilide and ethyl oxalyl-p-toluene sulphonamide.

The condensation of the acylbenzene V with the compound offormula R CZCZR, may be carried out merely by mixing the reactants together and heating, if desired, to a temperature of from 25 to 150C, preferably about 70 to 80C. In the case of the oxalate esters, the reaction is desirably carried out in the. presence of a condensation agent. Suitable agents include for example. metal alkoxides, such as sodium ethoxide, so-

dium hydride, sodamide or metallic sodium. The condensation agent may be formed in situ, for example by the use of ethanol as the reaction medium and the addition of metallic sodium. in some cases the alkali metal salt of the compound of formula V (that is when M is alkali metal) may act as part ofthe condensation agent required. Where a substituted dihalo-acetate is used. it is preferred to carry out the reaction in the presence of a finely divided metal catalyst, such as finely divided platinum group metal.

lfdesired. the reaction may be carried out in an inert solvent or diluent medium. such as diethyl ether. dioxan, ethanol, benzene. toluene, tetrahydrofuran. or mixtures thereof.

The reactants are conveniently employed in substantially stoichiometric proportions. If desired. an excess of either may be employed, for example in from I00 to 300 molar excess. When used, the condensation agent is desirably used in from 200 to 750 molar percent based on the amount of the acylbenzene of formula V used, preferably from 200 to 500 molar percent.

It will be appreciated that the condensation reaction is desirably carried out under substantially anhydrous conditions, that is in the absence of initial or added water.

The reaction mixture of the above reaction will usually contain the compound of formula ll, or a precursor thereof, though in some cases cyclisation of the product to the compound of formula I, or a salt or derivative thereof, may take place spontaneously. Cyclisation of the compound of formula I] may also be achieved in situ by acidifying the reaction mixture. It is usually preferred to recover the compound of formula II from the reaction mixture and to cyclise it in the presence of a cyclisation agent under substantially anhydrous conditions as described above. The compound may be recovered from the crude reaction mixture wherein it was prepared by conventional techniques. Thus, for example, the reaction mixture may be treated with ether to precipitate the intermediate, if this precipitation had not already been achieved by the use of ether as the reaction medium. The precipitate, after any further washing with ether, may be dissoved in water and acidified to yield the compound offormula [I which usually separates out and may be recovered by, for example, filtration, centrifuging, or by extraction with a suitable solvent such as chloroform or ethyl acetate and evaporation of the solvent. it may be preferred to omit the ether precipitation step and merely acidify the reaction mixture and recover the product by solvent extraction.

The compound of formula ll may also be prepared by the reaction of an acylbenzene of formula V wherein M is hydrogen or an alkali-metal cation with a dicarbonyl compound of formula RgCOCOR, wherein R and R have the values given above, except that one or both of R and R are halogen. Suitable dicarbonyl compounds for use in this case include oxalylchloride and compounds wherein R is chlorine or bromine and R is OH, alkoxy (e.g. methoxy or ethoxy) NH phenylamino or a p-toluene sulphonyl-amino group. The reaction using these halo compounds may be carried out in a manner such as sodium or potassium carbonate, sodium, sodamide and alkali metal alkoxides; and organic amines such as pyridine or triethylamine. The acid-binding agent is present in at least the theoretically stoichiometric amount to bind all the halogen in the dicarbonyl compound. It may be desired to use an excess of acidbinding agent, and, if desired, the acid-binding agent may be added to the reaction mixture in a series of additions over a period of time. In some cases the acidbinding agent may be used as the reaction medium. The reaction mixture from this process will usually contain the intermediate product of the formula COCli R OCOCOR' or a precursor or derivative threof, though in some cases rearrangement of this intermediate to yield the compound of formula Il may have occurred spontaneously. Rearrangement of the intermediate may also be achieved in situ by the addition of an alkali and heating. However it is usually preferred to recover the intermediate product from the reaction mixture and rearrange it, after any purification that may be desired, in a separate reaction step. The recovery and purification of the intermediate product may be achieved by conventional methods.

Rearrangement of the intermediate product may be achieved by heating the crude, or purified, recovered material under non-acidic conditions and preferably in an inert solvent or diluent medium such as benzene, dioxan, anisole or the like. The non-acidic conditions may be achieved by the presence ofa base, such as pyridine and potassium hydroxide or monoethylamine, or of an alkali such as sodium carbonate or potassium carbonate, sodium hydride, sodium alkoxides 'e.g. sodium methoxide, or metallic sodium. If desired, the rearrangement may be carried out under the influence of heat, for example at from ambient temperature to 100C, e.g. by heating on a steam bath and, where the reaction mixture permits it, under atmospheric reflux. Preferably the rearrangement is carried out under anhydrous conditions i.e. in the absence of appreciable amounts of initial or added water. The amount of alkali present may be from 100 to 1000 molar 70, based on.

the amount of the intermediate product being rearranged and may, if desired, be added in a single addition or in a series of additions over a period of time.

The compound of formula II or a derivative or precursor thereof, may be recovered from the reaction mixture in whic it was formed by conventional methods alkali metal alkoxide (e.g. sodium ethoxide), sodamide,

sodium hydride or metallic sodium.

The compounds of formula lll may be eyclised by treating the compound with a cyclisation agent at am bient temperature or above. Suitable cyclising agents include dehydrating agents such as phosphorus pentoxide, polyphosphoric acid, sulphuric acid. chlorsulphonic acid and other Lewis acids. In certain cases it is also possible to use glacial acetic acid containing a small amount of hydrochloric or hydrobromic acid. It will be appreciated that, since cyclisation is achieved in these cases by the use of dehydrating agents, the presence of added or initial water in the reaction mixture is undesirable. It is usually preferred to subject the compounds of formula ill to an initial drying step and to carry out the cyclisation reaction under substantially anhydrous conditions.

Alternatively, cyclisation may be achieved by converting the free carboxy groups of the compound of formula llI-into acyl chloride groups, for example, by treatment with PCL, or PCI,,, and subjecting the resultant acyl chloride to an internal Friedel Crafts reaction.

The compounds of formula III when R, is hydrogen may be obtained by the reaction of the phenol of formula:

v1 B OM (wherein M is hydrogen or an alkali metal cation) with an acetylene dicarboxylic acid or ester thereof under alkaline conditions to produce a product which, upon hydrolysis, yields the compound of formula II]. The acetylene dicarboxylic acid esters may be derived from alcohols having from I to 10 carbon atoms. However, since the ester moiety is to be eliminated, it is preferred to use simple esters derived for example, from methyl, ethyl, propyl, or butyl alcohols. It is preferred that both carboxylic acid groups on the acetylene dicarboxylic acid be esterified. In this process the ester and phenol are reacted, preferably in approximetely stoichiometric amounts, under alkaline conditions. These may be achieved by the presence of an organic base such as benzyl trimethyl ammonium hydroxide, or of an alkali metal hydroxide. However, it is convenient to have the alkali present in the form of an alkali metal salt, especially the sodium salt, of the reactant phenol, such a salt being considered as free phenol when assessing the amount of phenol present in the reaction mixture. Where this is done, the alkali metal phenate may conventiently be made in situ in the reaction mixture by the addition of metallic sodium. The alkali is believed to act catalytically and it is possible to use less than 100 molar percent thereof based on the phenol present. We prefer to use substantially 10 molar percent. It will be appreciated that the reaction, especially where the alkali metal phenate is formed in situ, is desirably carried out under substantially anhydrous conditions. It is also preferred to carry out the reaction in a solvent or diluent medium. Suitable media included, for example, excess of the reactant phenol, diphenyl ether, dioxan and H OOCC CCOO H wherein R is halogen and R is an R, group when R. and R together form a carbon to carbon bond; or. any two of R R R and R are halogen, one of the other two is hydrogen and the second is an R group. In this case the reaction is not an addition reaction but a condensation reaction which involves at some stage the elimination of the elements of a halogen acid from between the phenol and the halofumeric ester. This acid must be eliminated from the system and the reaction is therefore carried out in the presence of at least sufficient of an acid-binding agent to eliminate the elements of the halogen acid which will be formed during the overall process. The elements of the halogen acid are not necessarily eliminated in one step, but may be eliminated firstly as a proton and then as a halogen anion. The term acid-binding agent is therefore used in this context to denote both conventional acid-binding agents, such as pyridine and triethylamine, and materials which eliminate for example, first the hydrogen from the phenol (to form a phenate salt) and then are displaced from the phenate salt to form a salt with the halogen of the halofumaric acid ester. Apart from the use of a different acid ester reactant and the presence of the acid-binding agent, the process may be carried out in asimilar manner to that when an acetylene dicarboxylic acid ester is used. Since the acid-binding agent is usually also a strong alkali, there is generally no need to provide a separate strong alkali in the reaction mixture. As will be appreciated from the general formula for the acids which may be used to react with the phenot, the use of the monohalofumaric acid or precursors thereofperm its the introduction of an R, group into the molecule.

As indicated above, it is also possible to use compounds which yield the desired halofumaric acid esters under the conditions of the reaction with the phenol.

Such other compounds or precursors, include halo-- maleic acid esters and dihalosuccinic acid esters. When precursors are used, it may be necessary to provide extra alkali to ensure conversion of the precursor to the desired halofumaric acid ester. Such alkali may be merely an excess of the acid-binding agent.

The products obtained from the reactions outlined immediately above usually contain the compounds of formula lll in the form of their esters. The compounds of formula lll may be recovered from these products by acidification of the reaction mixture; subsequent hydrolysis of the esters by boiling with alkali and acidification to liberate the free acid, removal of organic solvent or diluent medium (if any) and extraction of the aqueous solution with. for example, ether which may thereafter be evaporated. The solvent extraction of the acid may be carried out as indicated, or may occur after hydrolysis of the ester of compound lll if desired. The product may, if necessary, be subjected to further purification, for example by extracting the ethereal solution with sodium bicarbonate and then precipitating the acid of formula lll by addition of dilute sulphuric acid.

The compounds of formula IV may be cyclised by treatment with an alkali or organic base in a suitable inert solvent to give the Z-carboxychromanone derivative. This may subsequently be converted into the Z-carboxychromone derivative by heating with selenium dioxide or other suitable dehydrogenation agents such as palladium black in an inert solvent as is detailed below. Simultaneous oxidation and cyclisation to the desired Z-carboxychromone derivative may be brought about by the introduction ofa suitable oxidant into the cyclisation stage (e.g. selenium dioxide in an inert solvent using bcnzyltrimethylammonium hydroxide as the cylising base).

Where non-oxidising conditions are used for the cyclisation step, the product will be the analogous chromanone compound from which the desired COOl-l ring compound may be prepared as detailed later.

The compounds of formula IV may be prepared by reacting an acylbenzene of formula V wherein M is hydrogen or an alkali-metal cation with glyoxalic acid or an ester thereof in the presence of a base (e.g. aqueous sodium hydroxide) or a mineral acid. A water miscible solvent, e.g. alcohol, may be added to facilitate the reaction.

Alternatively a phenol of formula V] wherein M is hydrogen is heated at a temperature of, for example, 25 to C with maleic anhydride in a solvent or diluent medium, such as nitrobenzene or carbon disulphide, in the presence ofa Lewis acid such as an excess of aluminium trichloride. The complex which is produced by this process may then be decomposed with a dilute mineral acid, such as hydrochloric acid, and the solvent removed, for example by distillation. The residue, which contains the compound of formula I-\/ wherein R" is OH, may be recovered using conventional techniques and then purified by, for example, recrystallisation. However, as indicated below the reaction may proceed to give a 2-carboxychromanone directly without isolation of an intermediate.

In the processes outlined above, we believe that the compounds ll to IV are all necessary intermediates in the conversion of the various starting materials to the compounds of formula I. However. in many cases the intermediates are formed under those conditions required to achieve cyclisation and therefore exist only transitorily. Whilst, for clarity, these processes have been described as if the compounds ll to IV were necessarily isolated prior to cyclisation, the invention embraces those processes wherein the intermediate under- COOH '0 ring may also be formed from an already present chromone ring, i.e. from a compound of formula wherein V is a group which is convertible to a -COOR group. Examples of suitable V groups include nitrile and ester groups which may be hydrolised to a carboxylic acidgroup, alkyl or substituted alkyl groups such as methyl, hydroxymethyl, halomethyl (e.g. chloromethyl, bromomethyl, dichloromethyl, trichloromethyl), acyl groups such as formyl or acetyl groups. and alkenyl and aryl alkenyl groups such as vinyl, w-trichloromethylvinyl and styryl groups, all of which are groups oxidisable or hydrolysable to a carboxylic acid group. The conversion of the V group to a COOH group or derivative thereof may be achieved using any of the known methods. 7

The compounds of formula Vll may be prepared by a variety of methods, many of which are closely analogous to the processes described above for the preparation and cyclisation of the compounds of formulae ll to IV except that in place of the starting materials ll, Ill

and W, compounds of the formulae l B C0 Cil"CO"V VIII and

$00 B 5 B 0 C Ix i 16 B1 B2 COCRfCllV are used and the at the final product requires conversion of the V group to the COOH group or derivative thereof. Such analogous processes may together be broadly described as a process for preparing a com pound of formula I by conversion ofa compound ofthe formula (wherein'A,, and A are the pairs ofgroups COCHR,. COD and OM; H and O-C(D)=CR,COOH. or -COCR=CHD and OM respectively wherein D is a COOR group or a group V convertible thereto, M is H, an alkali-metal cation or an alkyl group, M is H or an alkali metal cation and R and R have the values given above; one adjacent pair of the substituents B B B and B is the groups A and A which may have the values given above for A and A or may be the pair of groups A and A and the other two of the groups 8,, B B or B are hydrogen or substituents other than hydrogen) during which cyclisation of the groups A,, and A, and, if necessary, A and A takes place.

Thus the compounds of formula Vll may be prepared by cyclising a compound of formula Vlll under the conditions described above for the cyclisation of the compound of formula ll. ln some instances cyclisation may occur spontaneously.

The compounds of formula Vlll may themselves be prepared by condensing an acylbenzene of formula V with a compound of formula VCOR wherein V has the values given above and R is a group reactive with a hydrogen in the -COCH R group of the acylbenzene. Suitable compounds VCOR include esters of substitutedor unsubstituted acetic, acrylic and cinnamic acids, and the like, and amides or substituted amides. The condensation may be achieved by the method outlined earlier for the production of the compounds of formula ll from the acylbenzene V and the compounds R CZCZR,.

The compounds Vlll may also be prepared from the acylbenzene V and the compounds VCOR wherein R is halogen via, if necessary, the rearrangement of a compound of the formula:

B 'coca R B OCOV using conditions similar to those set out above for the preparation of the compounds of formula III by the analogous route.

Particular examples ofthe preparation of compounds VIII include the preparation of those compounds wherein V is a methyl group by reaction of an alkyl acetate. i.e. the compound VCOR;, wherein V is a methyl group and R is an alkoxy group. with an acylbenzene V under the condensation conditions outlined above for the preparation of compound II.

The 2-styryl compound, that is the compound of formula VIII wherein V is may be prepared from the acylbenzene V by reaction with sodium cinnamate and cinnamic anhydride or by reaction with a cinnamoyl halide, e;g. cinnamoyl chloride, in the presence of an acid-binding agent to yield the cinnamate ester of the acylbenzene, followed by rearrangement with a base, e.g. potassium carbonate, in the presence of an inert solvent such as toluene or benzene, to give a l, 3-diketone of the formula:

B CO ClI-CO-CIFCIIA r -B OH wherein Ar denotes a benzene ring.

From these examples of the preparation of the compounds of formula VIII it will be appreciated that certain of the processes for preparing the compounds of formulae II and VIII may together be broadly described as processes wherein an acylbenzene of formula V is reacted with a compound a W ((1),, -R

wherein R is a group reactive with an hydrogen in the -COCH R group of the acylbenzene, each Z is or one may be a (Hal) group, n is l or 2 and when n is 1, W is a D group i.e. a COOR group or a group V convertible thereto and when n is 2, W is an R group, i.e.' an OH group or a group convertible thereto.

The compounds of formula IX may be prepared by the reaction of a phenol of formula VI with a substituted acetylene monocarboxylic acid, or ester is manner similar to that used to prepare the compounds of formula III above. The acetylene monocarboxylic acids, or esters thereof, for present use have the general formggVQ Q- COORZ wherein V and R2 have the values given above. It is preferred that R; be a lower alkyl group such as a methyl or ethyl group. It is also possible to use precursors ofiacetylene monocarboxylic acids or esters, for example the mono-halo-ethylenic and dihalo-ethane analogues thereof.

The compounds of formula IX may be cyclised in a manner similar to that employed with the compounds of formula III. As with the compounds of formula II and VIII, the preparation of the compounds of formula III and IX may together be broadly described as a process wherein a phenol of formula VI is reacted with a compound of the formula wherein R R R R,,. R and D have the values given above and also the further value that when R,, and R,- together form a carbon to carbon bond.R,. and R may also form a carbon to carbon bond.

The compounds of formula X may also be prepared and cyclised in a manner similar to that used to prepare and cyclise the compound of formula IV. Thus. an acylbenzene of formula V may be reacted with an aldehyde of the formula OHCV, for example cinnemaldehyde, under substantially the same conditions as are used to prepare the compound of formula IV form glyoxallic acid. However, it may be preferred to employ acylbenzenes of formula V wherein M is an alkyl group and to dealkylate the reaction product to obtain the compound of formula X.

As with the other intermediate compounds, certain routes for the preparation of the compounds of formula IV and X may together be broadly described as comprising the reaction of an acylbenzene of formula V with a compound of the formulaOHCD wherein D has the values given above.

In addition to producing the compounds of formula VII by the methods outlined above, a number of other methods may be readily devised which do not necessarily pass through the intermediate compounds VIII, IX or X. Thus, the 2-formyl compound may be prepared by the reaction of an acylbenzene of formula V with a substituted acetic acid or ester thereof of the formula (R O) CH-COOR for example ethyl diethoxy acetate. In this case an acetal compound is produced as an intermediate, which may be hydrolised with, for example, a dilute mineral acid to yield the desired CHO group. Other routes which may be specified include: the condensation of a diketene with an appropriate enamine; the condensation of an alkyl alkoxalylacetate with an appropriate phenol or resorcinol in the pres-- ence of phosphorus pentoxide.

In addition to the direct conversion of a compound of formula VII into the desired compound of formula I, the V group in compounds of formula VII may be converted in known manner from one form of substituent into another more preferred substituent.

Thus, the compound of formula VII wherein V is a methyl group also serves as an intermediate in the preparation of a numer of other oxidisable derivatives. For example, the methyl group may be converted into the corresponding 2-halomethyl compound, eg by reaction with hydrogen chloride and manganese dioxide in boiling acetic acid to produce the Z-chloromethyl compound, or by reaction with bromine in acetic acid to yield the 2-bromomethyl compound. The 2-halomethyl compound may be oxidised to the corresponding 2- carboxylic acid using, for example, chromium trioxide as oxidising agent in the presence of acetic acid.

The Z-methyl compound may also be reacted. with p-nit rosodimethylaniline and the reaction product hydrolysed with dilute mineral acid to give the corresponding 2-formyl compound which may be oxidised to the corresponding 2-carboxylic acid using. for example, chromium trioxide as reagent.

Condensation of the Z-methyl compound with a benzaldehyde in the presenceof condensation catalyst gives the 2-styryl compound which may be oxidised to the corresponding Z-carboxylic acid using, for example, potassium permanganate. The 2 -formyl compound may also serve as a starting point for the preparation of the 2-cyano compound. Thus, the 2-formyl compound oximino compound which may, after dehydration to give the 2-cyano compound, be hydrolysed to the 2- carboxylic acid or amide thereof, under acid conditions.

As stated earlier the compounds of formula I may also be prepared by conversion of a chain COCH- R -CH(D)--O-- to the desired -CO-.CR =C- (COOH)O- chain. This conversion may go via a compound of formula Vll when the group D is a group V, or may procede directly to the compound of formula I or a derivative thereof. Thus, the compounds of formula I may also be prepared from corresponding chromanone compounds by dehydrogenation followed, or preceded, by oxidation or hydrolysis of any substituent in the 2-position if this is necessary. The dehydrogenation may be effected by, for example, the use of selenium dioxide, palladium black or chloranil. Alternatively, dehydrogenation may be carried out by bromination followed by dehydrobromination. Thus, the chromanone may be brominated using N- bromosuccinimide in an inert solvent or by treatment with pyridinium perbromi de in an inert solvent such as chloroform in the presence of a free radical catalyst such as benzoyl peroxide, to yield the 3,-bromo derivative which may be subsequently dehydrobrominated. The chromanones themselves may be obtained by the action of an fl-substituted B-chloropropionic acid or derivative thereof on resorcinol in the presence of a basic reagent followed by conversion ofthe acid function to the acid chloride and treatment with aluminium chloride in the presence of a suitable solvent (e.g. nitrobenzene); or by the action ofa phenol on a B-substituted acrylonitrile, e.g. propenylnitrile with subsequent hydrolysis and cyclisation of the product. As indicated above, cyclisation of the intermediates IV and X may lead to the production of a corresponding chromanone compound, which may then be converted as outlined above to the desired chromone compound.

In addition to the above outlined methods for preparing the compounds of formula I via the intermediates II to IV and VII to X, other methods may be devised which do not necessarily produce any of these intermediates. Thus, an acetylhalide, acetic anhydride or acetic acid may be condensed with an oxalate ester ofthe type R,,,OOC(IOOR, wherein R is an aryl group and R is an alkyl or an aryl group, the condensation being carried out in the presence of a Lewis acid. The oxalate ester may itself be obtained by the esterification of a phenol of formula V] with the appropriate oxalyl halide. Alternatively the compounds of formula I may be obtained by reacting a phenol of formula V] with ethyl 15 may be reacted with hydroxylamine to yield the 2- f COOR is reacted wit h a fu ran of the formula which may be converted, for example by dehydration, to the compound.

rings may be introduced in separate steps or in the same step. Where they are both ,to be introduced together, the two pairs of groups A and A will have the same values, appropriate to the method used to introduce the rings. Thus, where'condensation with an acylbenzene forms one of the steps required, one group in each pair will be a -COCl-l R group and the other will be an OM group.

From the 'above examples of the conversion of the starting materials into the desired COOli compounds, it will be seen that many of these routes may be together broadly described as the conversion of compounds wherein A, and A together form the groups --OM and H, D or COD; H and OCD=CR,CO()R -OCOCOR" and H or COCH R, respectively wherein D is a group -CH R,, -OR -CHR,COD or CR =CHD and R, R R D and M have the values given above; or wherein A, and A together form the chains CO-CR =O(D) having the values set out above.

The processes outlined above may produce the free acids of formula I or may yield derivatives thereof. It is also within the scope of the present invention to treat the product ofany of the above processes, after any isolation and purification steps that may be desired, in order to liberate the free acid therefrom or to convert one form of derivative into another. The methods used to free the acid, convert one derivative into another and to isolate and purify any product may be those con ventionally used.

Furthermore, it is also within the scope of this invention to introduce the substituents P, Q, R, T, P, Q, R, and T after formation of one or both the block or shield sites or groups which might be detrimentally affected during the introduction of the ring or rings. Such shielding or blocking groups include, for example, amino, substituted amino e.g. acylated amino, carboxyl, SO H, tert. butyl, cyano or nitro groups. These groups may be removed after introduction ofthe ring or rings to leave unsubstituted positions which may, if desired, thereafter be substituted.

Certain of the intermediates formed in the production of the compounds of formula I are, we believe,

novel. The invention therefore also provides as novel compounds, compounds ofthe general formulae ll, III, IV, Vll, Vlll, IX and X set out above, except those wherein A and A are the pairs of groups OM and H or COCH R,; notably those compounds wherein one pair ofthe groups A, and A, forms the chain COCR =C(- D)-O or -CO-CHR,CH(D)O. Preferred compounds are those wherein each pair of groups A and A are the same, other than a chain COCR =C- (COOH)O-.

The invention will be illustrated by the following Examples in which all parts and percentages are by weight unless otherwise stated:

EXAMPLE 1 4, l0-Dioxo-5-methoxy-2,8-dicarboxy-4H,lOH-benzo (l,2-b:-3.4-b') dipyran a. 4,lO-Dioxo-S-methoxy-2,8-dicarboxy-4H.10H- benzo (l,2,-b:-3,4-b) dipyran, monohydrate To a stirred solution of sodium ethoxide in ethanol, prepared from 3.04 parts of sodium and 40 parts of ethanol, was added a slurry of 3.7 parts of 2,4-diacetyl-5- methoxy-resorcinol and 12.05 parts of diethyl oxalate in 20 parts of ethanol and 50 parts of diethyl ether. The mixture was stirred and heated under reflux for 4 hours.

Diethyl ether and water were added, and the aqueous layer was separated and acidified with dilute hydrochloric acid. The aqueous solution was extracted with ethyl acetate dried over sodium sulphate, filtered and evaporated to dryness to leave a brown oil.

This oil was dissolved in boiling ethanol and 0.5 parts of concentrated hydrochloric acid were added. The solution was heated under a reflux for 10 minutes and the solvent was then removed under reduced pressure to leave a brown oil.

This oil was triturated with ether to give a solid which was shown by thin layer chromatography to be a mixture of acid and ester. The solid was heated in aqueous sodium bicarbonate solution until it had all dissolved. This solution was cooled and acidified with dilute hydrochloric acid to give 0.96 parts of 4, lO-dioxo-S- methoxy-2,8-dicarboxy-4H,lOH-benzo( l ,2-b:-3,4- b)dipyran, monohydrate as a pale brown solid, melting point 262-263C(d).

Analysis:

Found: c, 51.7%; H, 3.02%. C,,-,H,.O,,.H2O requires: C, 51.5%; H, 2.86%.

b. 4,lO-Dioxo-S-methoxy-2,8-dicarboxy-4H,10H- benzo (l,2-b:-3,4-b)dipyran, disodium salt A solution of 0.83 parts of 4, lO-dioxo-S-methoxy- 2,8-dicarboxy-4H, l0H-benzo (l,2-b:3,4-b')dipyran monohydrate and 0.4 parts of sodium bicarbonate in 50 parts ofwater was freeze-dried to give 0.83 parts of 4,l O-dioxo-S-methoxy-2,8-dicarboxy-4H, IOH-benzo (l,2-b:-3,4-b)dipyran disodium salt as a pale yellow solid.

EXAMPLE 2 4, l O-Dioxo-Z,8-dicarboxy-5-hydroxy-4H, l OH-benzo 1,2-b: 3,4-b') dipyran a. 4,l0-Dioxo-2,8-dicarboxy-5-hydroxy-4H,lOH-benzo (l,2-b: 3,4-b)dipyran monohydrate.

A solution of 0.55 parts of 4, l0-dioxo-2,8-dicarboxy 5-methoxy-4H,l0H-benzo l,2-b: 3,4-b)dipyran monohydrate (Prepared as in Example 1) in a mixture of 7 parts of hydrogen bromide-acetic acid (45% w/v) and 7 parts of glacial acetic acid was refluxed for 1 /2 hours. During this time, a solid separated out of the reaction mixture. The mixture was poured into 200 parts of water and the solid precipitate was filtered off.

The solid was dissolved in aqueous bicarbonate solution and the solution treated with charcoal and filtered. Acidification of the bicarbonate solution with dilute hydrochloric acid gave 0.3 parts of 4,l-dioxo-2,8- dicarboxy--hydroxy-4H,lOH-benzo (1,2-b: 3,4-b') dipyran monohydrate as a pink solid, melting point 300-302C (d).

, Analysis:

Found: C, 49.8%; H. 2.l4/. C H O H O requires: C. 50.0l/r; H. 2.4%.

b. 4,lO-Dioxo-Z,8-dicarboxy-5-hydroxy-4H,l0H-benzo (1,2-b: 3,4-b) dipyran disodium salt A solution of 0.238 parts of 4,l0-dioxo-2,8- dicarboxy-5-hydroxy-4H, l OH-benzo (1,2-b: 3,4- b')dipyran monohydrate and 0.l 13 parts of sodium bicarbonate in 30 parts of water was freeze-dried to give 0.23 parts of 4,lO-dioxo-2,8-dicarboxy-5-hydroxy- 4H,l0H-benzo (1,2-b: 3,4-b)dipyran disodium salt as a buff coloured solid.

EXAMPLE 3.

4, l0 Dioxo-5-methyl-2,8-dicarboXy-4H, l0H-benzo (l,2-b:3,4-b') dipyran To a solution of 3.l parts of anhydrous orcinol in- 50 parts of anhydrous dioxan were added 0.23 parts of so dium. The mixture was stirred and heated until the sodium had dissolved. The stirred solution was then treated dropwise with a solution of 7.5 parts of dimethyl acetylene dicarboxylate in 20 parts of anhydrous dioxan. After stirring and heating on a steambath for 15 minutes, the mixture was cooled and acidified with 9 parts of 10% w/v sulphuric acid solution. It was then treated with 25 parts of 25% w/v sodium hydroxide solution; heated on a steam-bath for one hour; cooled; acidified with 10% w/v sulphuric acid solution; and the dioxan was then distilled off. The mixture was extracted with ether and the ether evaporated to leave a yellow solid which was crystallised from water to give 1.0 parts of oreinol di(trans, 1,2-dicarboxy vinyl) ether, melting point, 260-26lC.

Analysis Found: C, 50.92%; H, 3.59%. C H Om requires: C. 51.15%; H, 3.4l'7z.

The structure was confined by nuclear magnetic resonance spectrum.

A mixture of 0.5 parts of orcinol di(trans, 1.2- dicarboxy vinyl) ether and parts of polyphosphoric acid was stirred and heated at l l0l20 for 3 hours. The mixture was cooled and diluted with ice-water. The supernatant liquid was decanted off and the precipitatedsolid was filtered off, washed with water and dried in the oven to leave 0.3 parts of 4,10-dioxo-5- methyl-2,8-dicarboxy-4H, l0H-benzo (1,2-b; 3,4-b) dipyran sesquihydrate, melting point, 285-286 C. (Decomp).

Analysis Found: C, 49.8%; H, 2.14%. C H,,O,,.H O requires: C, 50.01%; H. 2.4%.

The material was shown to be identical with the free acid obtained by reaction of diethyloxalate and 2,4- diacetylresorcinol using the method of Example I by comparison'of melting points and infra-red spectra. The mixed melting point gave no depression.

EXAMPLE 4 2,8-Dicarboxy-4,l0-dioxo-5-methoxy-4H,IOH-benzo (1,2-b: 3,4-b') dipyran A mixture of 5-methoxy-2,4-diacetylresorcinol (20 parts) and ethyl ethoxydichloracetate (52 parts) was heated at 150 to 170C for 5 hours. After evaporating off any volatile material under reduced pressure, a mixture was obtained which was hydrolysed by dissolving in glacial acetic acid containing 17% of concentrated hydrochloric acid (500 parts total) and refluxing for 4 hours. After cooling, a solid was obtained. This solid was filtered off, washed well with water and purified by dissolving in aqueous sodium bicarbonate, treating the hot solution with charcoal, filtering and precipitating with concentrated hydrochloric acid. The product, 2,8-dicarboxy-4,l0-dioxo-5 methoxy -4H, lOH-benzo (l,2-b; 3,4-b') dipyran monohydrate, was shown to be identical with the product of Example 1(a).

EXAMPLE 5 2,8-Dicarboxy -4,l0-dioxo-5-methoxy -4H,l0H-benzo (1,2-b; 3,4-b') dipyran monohydrate A solution of 5methoxy-2,4-diacetylresorcinol l part) and ethyl N-toluene-p-sulphonyloxamate l0 parts) in 80 parts by volume ofdry ethanol and 10 parts by volume of dioxan, was added to a solution of 1.3 parts of sodium in 100 parts by volume of ethanol. The resultant mixture was heated under reflux for 20 hours. After cooling the mixture, a large excess of ether (500 parts) was added and the mixture was extracted with water. The aqueous extract was acidified and extracted into chloroform and filtered to remove by'product bis (N,N toluene -p-sulphonyl) oxamide. The chloroform solution was dried and evaporated to dryness, yielding a sticky solid which was washed several times with ether, the ethereal extracts being separated by decantation, to leave a further amount of his (N,N toluene-psulphonyl) oxamide. The ethereal extracts on evaporation gave an oil which was dissolved in ethanol (20 parts) containing a few drops of concentrated hydrochloric acid. This solution was refluxed for 15 minutes and the solvent removed in vacuo to yield a brown oil.

Thin layer chromatography showed that this oil was probably a mixture ofthe desired acid and its ester. The

mixture was therefore hydrolysed with aqueous sodium bicarbonate. Heating of the hydrolysis mixture was continued until complete solution was achieved. The

EXAMPLE 6 2,3-Dicarboxy-4, lO-dioxo-5-methoxy-4H, IOH-benzo (1,2-b: 3,4-b) dipyran monohydrate Ethyl oxalylchloride (8 parts) was added slowly to a mixture of 2,4-diacetyl-S-methoxyresorcinol (2.5 parts) and anhydrous pyridine (10 parts) cooled in ice. The mixture was kept at room temperature for 24 hours and then heated for 30 minutes on a steam bath. After cooling and pouring onto a mixture of ice and hydrochloric acid, an oil was obtained which was extracted with chloroform, washed and the chloroform solution then dried over sodium sulphate. After filtration and removal of the solvent. the residue was crystallised from ethanol to give 2,8-dicarboxy-4, lO-dioxo-S- methoxy -4H, IOH-benzo (l,2-b: 3.4-b') dipyran monohydrate which was shown to be identical with the product of Example l(a).

EXAMPLE 7 2,8-Dicarboxy-4, l-dioxo-5-methoxy-4H, IOH-benzo (l,2-b: 3,4-b) dipyran monohydrate.

A mixture of phloroglucinol monomethyl ether (2 parts) and ethyl ethoxalylacetate parts) in diphenyl ether (30 parts) was heated for 4 hours at 150C. The reaction vessel was fitted with an air condenser, so that volatile reaction products, such as water and ethanol, could escape from the reaction mixture. After cooling, the reaction mixture was triturated with an excess of petroleum ether (b.p. 60-80C) several times, to leave a sticky gum. Aqueous sodium bicarbonate was added to this gum and the mixture heated on a steam bath until solution ofthe gum was achieved. Acidification of the solution gave 2,8-dicarboxy-4, l0-dioxo-5- methoxy-4H, IOH-benzo 1,2-b: 3.4-b) dipyran monohydrate which was shown to be identical with the product of Example 1(a).

EXAMPLE 8 2,8-Diethoxycarbonyl-4, l0dioxo-4H, IOH-benzo (1,2-b: 3,4-b) dipyran Resacetophenone (7.6 parts) and dimethyl acetylene dicarboxylate parts) were mixed together and 3 drops of benzyltrimethylammonium hydroxide (40% aqueous solution) were added. The resulting solution was heated on a steam bath for 1 hour and then cooled, treated wtih sodium hydroxide (45 parts of 25% aqueous solution) and heated on a steam bath for 3 hours. The mixture was then cooled and acidified with sulphuric acid H SOQ. A precipitate was slowly deposited, which was filtered off, washed with water and crushed to leave a fawn powder. This powder was crystallised from water to give 3.5 parts of 3-hydroxy-4- acetylphenoxyfumaric acid hemi-hydrate.

Analysis;

Found: C. 52.8%: H. 3.89

Melting point: 217C (d).

A mixture of this material and concentrated sulphuric acid (18 parts) was stirred until a clear solution was obtained. The solution was then heated on a steam bath for 10 minutes, cooled and poured onto ice. A fine green precipitate was obtained which settled under gravity. This precipitate was filtered off, washed with water and dried. The dried powder was crystallised from ethanol to give 0.9 parts of 5-hydroxy-6- acetylchromone-Z-carboxylic acid; whose structure was confirmed by NMR evidence.

Analysis:

Found: C, 58.0%; H, 3.26%. C,,H,,O requires: C, 58.1%; H, 3.23%.

Melting point 262C (d).

This product (0.5 parts) was mixed with diethyl oxalate (5 parts by volume) in dry ethanol (20 parts by volume) and the mixture added to a solution of sodium (0.5 parts) in dry ethanol (50 parts by volume). The resultant solution was stirred and heated under reflux for 16 hours, cooled and poured into a large volume of ether. The mixture was extracted several times with water and the aqueous extracts acidified. The acidified aqueous extracts were then extracted with chloroform (three 50 part lots). The chloroform extracts were washed with water, dried and evaporated to dryness leaving an oil. This oil was dissolved in dry ethanol (20 parts) and the solution saturated with hydrogen chloride by passing a stream of dry hydrogen chloride through the solution. This mixture was kept overnight and then refluxed for 1 hour. The ethanol was evaporated and iced water added to the residue to give a sticky solid. The water was decanted and the solid crystallised from ethanol to give 2,8-diethoxycarbonyl-4, lOdioxo-4H, IOH-benzo (l,2-b: 3,4-b') dipyran which was shown to be identical to the ester obtained when 2,4-diacetylresorcinol was reacted with diethyl oxalate using the process of Example 1.

EXAMPLE 9 2,8-Dicarboxy-4, 6-dioxo-l0-nitro-4H, 6H-benzo (1,2-b: 5,4-b') dipyran Powdered aluminium chloride (15 parts) was added with stirring to a solution of 2-nitroresorcinol (3.5 parts) and maleic anhydride (5.5 parts) in ethylene dichloride (200 parts). After standing at room temperature for 20hours, the mixture was warmed to C for 1 hour, cooled and filtered to give a yellow residue. This residue was added with stirring to a mixture of crushed ice (20 parts), concentrated hydrochloric acid (10 parts) and chloroform parts). The mixture was allowed to separate into two layers. After 30 minutes the organic layer was removed, the aqueous layer extracted with further lots of chloroform and the chloroform extracts combined with the organic layer. The combined organic layer was dried over sodium sulphate and the chloroform evaporated off in vacuo to give a reddish brown oil which was taken up in amyl alcohol (50 parts) and selenium dioxide (3 parts) was added. The mixture was refluxed for 18 hours. The inorganic materials were then removed by centrifuging and decanting. The organic layer was then steam distilled to remove the solvent and purified by dissolution in sodium bicarbonate, treatment with charcoal, filtration and precipitation with concentrated hydrochloric acid to give 2,8-dicarboxy-4. 6-dioxo-l0-nitro-4H, 6H- benzo (l,2-b; 5,4-b) dipyran which was identical to the compound obtained when 2,4-diacetyl-6 nitroresorcinol was reacted with diethyl oxalate using the method of'Example 1.

EXAMPLE l0 2,8-Dicarboxy-4, 6-dioxo-l0 methyl-4H, 6H-benzo (l,2-b: 5,4-b) dipyran a. 3,7-Diacetyl-2,8-dimethyl-4,6-dioxo-l0-methyl-4H,

mixture was cooled and then poured onto ice. A brown oil was precipitated and the aqueous layer was decanted therefrom. The oil was washed with water. Hydrochloric acid 150 parts, HCl) was added to the oil and the mixture heated to boiling. On cooling, a brown crystalline solid was obtained which was filtered off, suspended in boiling ethanol for 15 minutes and, after cooling filtered off to yield 3, 7-diacetyl-2,8- dimethyl-4, 6-dioxo-l0-methyl-4H, 6H-benzo (l.2-b: 5,4-b) dipyran.

Analysis:

Found: C, 67.5%; H, 4.56%. C H O requires: C, 67.0%; H, 4.71%.

Melting point 280-285C. b. 2,8-Dimethyl-4,6-dioxo-l0-methyl 4H, 6H-benzo (l,2-b: 5,4-b') dipyran A mixture of 3,7-diacetyl-2,8-dimethyl-4, 6-dioxo -l0-methyl-4H, 6H-benzo (1,2-b: 5,4-b') dipyran (0.9 parts as prepared above), sodium carbonate (2.0 parts) and water (40 parts) was heated under atmospheric reflux for 1.5 hours. The resulting solution was acidified and the precipitated solid was filtered off, washed with water, and crystallised from ethanol to give 2,8- dimethyl-4,6-dioxo'-lO-methyl-4H, 6H-benzo (l,2-b: 5,4-b') dipyran (0.5 parts) as a yellow solid. c. 2,8-Dicarboxy-4, 6-dioxo-lO-methyl-4H, (H-benzo (1,2-b: 5,4-b) dipyran hemihydrate Finely divided selenium dioxide (l.2 parts) was added to a mixture of 2,8-dimethyl-4,6-dioxo-l0- methyl-4H, 6H-benzo (1,2-b: 5,4-b) dipyran (1.0 part as prepared above) and dioxan parts). The resultv ing mixture was heated under atmospheric reflux for 8 hours. After cooling the reaction mixture, the selenium precipitate was filtered off and the solvent removed from the filtrate by evaporation in vacuo. The solid residue was extracted with aqueous sodium bicarbonate. The extract was acidified with dilute hydrochloric acid and the precipitated solid filtered off to give 2,8- dicarboxy-4,6-dioxo-l0-methyl-4H 6H-benzo (l,2-b: 5,4-b') dipyran hemihydrate. The product had a melting point of 292-294C and was shown to be identical to the product obtained by the reaction of 4,6-diacetyl- Z-methylresorcinol with diethyl oxalate using the process of Example 1.

EXAMPLE 1] 2,8Dicarboxy-4,6-dioxo-lO-methyl-4H, 6H-benzo (l,2-b: 5,4-b') dipyran a. 2,8-Dim ethyl-4,6-dioxol O-methyl-4H, 6H-benzo (1,2-b: 5,4-b) dipyran A mixture of powered sodium (2.3 parts), 4,6- diacetyl-2 methylresorcinol (2.08 parts) and ethyl acetate (70 parts) was stirred and heated under gentle atmospheric reflux for 4 hours. The resulting solution ture on cooling was filtered off to give 2,8-dimethyl-4,

6-dioxo-l0-methyl-4H, oH-benzo (1,2-b: 5.4-b') dipyran which was identical to that obtained in step b of Example 10.

b. The 2,8-dimethyl-4.6-dioxo-l0-methyl-4H, 6H- benzo (1,2-b: 5,4-b) dipyran was oxidised to the corresponding 2,8-dicarboxyl-4,6-dioxo-l0-methyl-4H.6H- benzo (l,2-b: 5,4-b') dipyran hemihydrate by the method of step (c) of Example l0.

EXAMPLE l2 2,8-Dicarboxyl-4, 6-dioxo-l0 -methyl-4H, 6H-benzo (1,2-b: 5,4-b) dipyran a. 2,8-Distryl-4, 6-dioxo-l0-methyl-4H. 6H-benzo l .2- b: 5,4-b') dipyran A slurry of 2,8-dimethyl-4,6-dioxol0-methyl-4H. 6H-benzo (l,2-b: 5,4-b') dipyran (2.6 parts, prepared as in Example 10 or 1 l) and benzaldehyde (2.12 parts) in ethanol (20 parts) was added to a stirred solution of sodium ethoxide in ethanol, which had been prepared by dissolving sodium (0.46 parts) in ethanol (20 parts). The mixture was stirred and heated under atmospheric reflux for 4 hours and then left to stand at room temperature for 18 hours. The supernatant liquor was decanted from the brown oil which had precipitated. The oil was washed by trituration with ether and not purified further, to yield 2,8-distyryl-4,6-dioxo-l0-methyl- 4H, 6H-benzo (l,2-b: 5,4-b) dipyran. b. 2,8-Dicarboxyl-4, 6-dioxo-l0-methyl-4H, 6H-benzo (1,2-b: 5,4-b) dipyran hemihydrate The crude 2,8-distyryl-4, 6-dioxo-lO-methyl-4H, 6H- benzo (1,2-b: 5,4-b) dipyran obtained by the above process was dissolved in pyridine (50 parts) and aqueous potassium permanganate solution parts of 5% solution) was added. The mixture was stirred at room temperature for several hours. The presence of excess permanganate was checked from time to time and further amounts of 5% solution were added as required. When no further oxidation took place, the solution was acidified with dilute hydrochloric acid and decolourised with sulphur dioxide. The precipitate was filtered off, washed with water and extracted into aqueous sodium bicarbonate solution. Upon acidification of the solution, a precipitate was formed which was filtered off and dried to yield 2,8-dicarboxy-4, 6-dioxo-l0- methyl-4H, 6H-benzo (1,2-b: 5,4-b') dipyran hemihydrate, which was shown to be identical with the product of Examples 10 and l 1.

EXAMPLE l3 6-Bromo-2,8-dicarboxy'-4,l0-dioxo-5-hydroxy-4H,

IOH-benzo 1,2-b: 3,4-b) dipyran Found: C.57.0%;H.3.8l'/1. C H O, requires: C, 57.7%; H, 3.77%.

Melting point 171C.

b. 6-Bromo-2,8-diethoxycarbonyl-4,10-dioxo-S- hydroxy-4l-l, 10H-benzo (1,2-b: 3,4-b) dipyran To a solution of 2.8-Diethoxycarbonyl-4, l0-dioxo-5- hydroxy-4H, IOH-benzo (1,2-b: 3,4-b) dipyran (0.5 parts as prepared above) in glacial acetic acid (10 parts) was added a solution of bromine (0.1 parts) in glacial acetic acid. The solution was heated at 100C for 6 hours and then the acetic acid was evaporated. The oily product was triturated with cold ethanol and the resulting solid was filtered off to give 6-bromo-2,8- diethoxycarbonyl-4, 10-dioxo-5-hydroxy-4H, 10H- benzo (1,2-b: 3,4-b) dipyran (0.4 parts) as a pale brown solid, melting point 199-202C.

c. 6-Bromo-2,8-dicarboxy-4, IO-dioxo-S-hydroxy- 4H, 1OH-benzo (1,2-b: 3,4-b') dipyran trihydrate A solution of 6-bromo-2,8-diethoxycarbonyl-4, 10-dioxo-5-hydroxy-4H, 10H-benzo (1,2-b: 3,4-b) dipyran (0.4 parts as prepared above) in aqueous ethanol (25 parts) was hydrolysed with sodium bicarbonate. Acidification of the bicarbonate solution with dilute hydrochloric acid gave 6-bromo-2,8-dicarboxy-4, l0-dioxo-5-hydroxy-4H, 10H benzo (1,2-b: 3,4-b') dipyran trihydrate (0.1 parts) melting point 312C(d).

Analysis:

Found: C, 37.0 C H,;O Br3H:O requires: C. 37.25:

d. 6-Bromo-2,8-dicarboxy-4,10-dioxo-5-hydroxy-4H, lOH-benzo (1,2-b: 3.4-b') dipyran disodium salt A solution of 6-bromo-2,8-dicarboxy-4. IO-dioxo-S- l0 hydroxy-4H, 10l-l-benzo (1,2-b: 3,4-b') dipyran trihy- EXAMPLE 14 The processes described in Examples 1 to 13 were 20 repeated using different reactants and Table 1 sets out the products obtained, the Example number of the process route employed and the physical characteristics ofthe products, were measured.

TABLE 1 Ex. Physical data, where measured Name of Compound No. Melting Analysis Found 01 Pre- Point parative in "C C7t H7: Other 7:

Route 4,6di0x02,8-diethoxycnrbonyl-4H,bH-benzo(1.2-b;5.4-b')dipyran 1 225-6 60.34 3.85 4.6-dioxo-2.S-dicarboxy-4H.6H-bcnzo(1,2-b:5,4-h')dipyramdisodium salt 1 46.6 1.67 4.1(l-dioxn-Z.8-diethoxycarhonyl-4H,l0H-bcnzu(1,2-b;3.4-h')dipyran 1 183-4 60.79 3.74 4.1U-Dioxo-Z,8-dicarboxy-4H.IOH-hcnzo l ,2-b;3,4-b'), dipyran disodium salt 1 44.6 2.09 5-Benzyloxy-4,l0-dioxo-2,8-dicthoxycnrbunyl-4H.IOH-benzo (1,2-b;3,4-b') dipyran 1 210-212 64.8 4.21 5-Benzyloxy-4.10 dioxo-Z,8-dicarboxy-4H,NIH-benzo (1 .2-h;3,4-b') dipyran scsquihydrate 1 272-5 57.6 3.42 5-Benzyloxy-4.1U-dioxo-Z,8-dicarboxy-4H.IOH-benzo (l .2-b:3.4'b') dipyran. disodium salt 1 l 4,10-Dioxo-S-methyl-2,8-dicarboxy-4H IOH-benzo (1 ,2-b;3,4-b') dipyran sesquihydrate 1 (via ethyl 287 52.22 3.02

ester) (decomp) 4,10-Dioxo-S-methyl-2,8-dicarboxy-4H.1OH-benzo(1,2-b;3,4-b') dipyran disodium salt 1 5-Methoxy-4,6-dioxo-2,8-diethoxycarbonyl-4H,6H-benzo (1,2-b:-5.4b') dipyran 1 227-8 59.0 4.20 5-Methoxy-4,6-dioxo2.8-dicarboxy-4H .H-benzo (1 .2b:-5.4b') dipyran disodium salt 1 11.93 Na 4,10-Dioxo-fi-ethyl-2,8-dicarboxy-4H,IOH-benzo (1.2-b: 3,4-b) dipyran monohydrate 1 (via ethyl 282 55.6 3.23

ester) 4,10-Dioxo-fi-ethyl-Z.8-dicarboxy-4H,lOH-benzo (1.2b: 3,4-b') dipyran disodium salt 1 4,6-Dioxo-2.8-dicarboxy'10-methyl-4H.6H-benzo (1,2-b: 5.4-b) dipyran hemihydrate 1 (via ethyl 293-4 55.78 2.51

ester) 4,6'Dioxo-2.8-dicarboxy-10-methyl-4H.611-benzo(1.2-b: 5.4-b) dipyran disodium salt 1 4,6-Mono-2,8-dicarboxy-10-ethyl-4H.6H-benzo(1,2-b:5,4;b') dipyran hemihydrate l 315 57.2 2.95 4,6-Dioxo-2,8-dicarboxyl 0-ethyl-4H, 6H-benzo (1 ,2-b:5,4-b) dipyran disodium salt 1 4.6-Dioxo-2.tl-diethoxycarbonyl-10-ethyl-4H, 6H-benzo(1,2-b: 5.4-b)dipyran g 1 189-91 61.9 4.98 4,6-Dioxo-2,S-diethoxycarbonyl-10-nitro-4H,6H-benzo(1,2-b:5.4-b) dipyran 1 215 53.9 3.14 3.36N 4,6-Dioxo-2,8-dicarboxy-10-nitro-4H, 6H-benzo(1.2-b: 5,4-b') dipyran hemihydrate 1 225-7 44.1 2.31 3.5N 4,6-Dioxo-2,8-dicarboxy-lll-nitro-4H,6H-bcnzo(1.2-b: 5.4-b') dipyran disodium salt 1 6,1ll-dicarboxy-4-methyl-2,8.l2-triox0-2H.8H.lZH-henzo(1.2-b: 3.4-b: 56b") tripyrantrihydratc 1 263-7 49.6 2.96 .1(l-dicarboxy-4-methyl-2,8. l 2-trioxo-2H,8H,lZH-bcnzo l ,2-b: 3,4-b: 5,-h") tripyran disodium salt I 6-bromo-2.8-diethoxycarhonyl-4, l 0-dioxo-5-hydroxy-4H l ()H-hcnzo 1 .2-11: 3 .4-hl dipyran 1 199-202 46.5 2.87 6-bromo-2,8-dicarboxy-4,1(1-dioxo-5-hydroxy-4H,ltlH-benzo(l.2-b:3,4-b'l dipyran dihydratc l 312 (d) 37.0 1.82 6-bromo-2,8-dicarboxy-4,10-dioxo-5-hydroxy-4H,IOH-benzo (1,2-b:3.4-h) dipyran disodium salt 1 4,10-dioxo--chloro-2,8-dicarboxy-4H,1OH-benzo (1.2-b:3.4-b) dipyran monohydrate V 2 286-7 47.1 1.62

Ex. Physical data. where measured Name of Compound No. Melting Analysis Found of Pre- Point parative in "C C'R' HQ Other '7:

Route 4, l -dioxo-6-chloro-2.8-dicarboxy-4H .l OH-behZo (l .2-b13 .4-b) dipyran disodium salt 2 4.IO-dioxo-Z.8-dicarboxy--allyloxy-4H,lOH-benzo (l .2-b:3.4-b') dipyran hemihydrate 4.l0-dioxo2.8-dicarboxy-5-allyloxy-4H, IOH-benzo (I .2-b:3.4-b') dipyran disodium salt EXAMPLE l5 Found: C, 67.0;

H. 7257:. C H O requires: C. 6 8; H. 7

b. lO-Butyl-2,8-Diethoxycarbonyl-4,6-Dioxo-4H,6H- Benzo [l,2-b: 5,4-b] Dipyran To a stirred solution of 2.] parts of sodium in 60 parts of dry ethanol was added a slurry of 2.5 parts of 4,6- diacetyI-Z-n-butylresorcinol and 7.3 parts of diethyl oxalate in 50 parts of dry ethanol. The mixture was stirred and heated under reflux for 4 hours.

After cooling, the mixture was poured into a separating funnel containing ethyl acetateand dilute hydrochloric acid. The ethyl acetate layer was separated, dried over sodium sulphate and evaporated to leave an oil.

This oil was dissolved in 100 parts of ethanol containing 2.0 parts of concentrated hydrochloric acid and the solution was heated under reflux for 30 minutes. The volume was reduced to 50 ml. then the solution was allowed to cool whence a solid crystallized. This solid was recrystallised from ethanol to give l0-butyl-2,8-

diethoxycarbonylfl,6-dioxo-4H,6H-benzo [1,2-b: 5.4-

b] dipyran as colourless needles, melting point l55-l57C. Analysis Found: C. 63.7; H. 5.33%. C H O requires: C. 63.76; H. 5.35%.

c. l0-Butyl-2,8-Dicarboxy-4,6-Dioxo-4H,6H-Benzo [1,2-b: 5,4-b] Dipyran Hemihydrate A solution 2.0 parts of l0-butyl-2.8- diethoxycarbonyl'4.6-dioxo-4H.6H-benzo [l.2-b: 5.4- b'] dipyran and 1.22 parts of sodium bicarbonate in aqueous'ethanol was heated till'thin layer chromatography showed that the ester had been completely hydrolysed. The solution was then cooled and acidified with dilute hydrochloric acid to give a white precipitate. This solid was filtered off and boiled with ethanol. This procedure left 0.8 parts of l0-butyl-2.8-dicarboxy-4,6- dioxo-4H,6H-benzo [1,2-b: 5,4-b'] dipyran hemihydrate as the insoluble product, melting point 3 l4C (d).

Analysis Found: C.

H. 3.9%. C,,.H O,..V2H O requires: C. H. 4 I71.

EXAMPLE l6 2.6, l 0-Tricarboxy-4,8, l 2-Trioxo-4H,8H, l ZH-Benzo [1,2-b: 3,4-b': 5,6-b] Tripyran a. 2.6,lO-Tricarboxy-4,8,l2-trioxo-4H,8H.lZH-Benzo [1,2-b: 3,4-b: 5,6-b"] Tripyran Hemihydrate To a stirred solution of 2.76 parts of sodium in 50 parts of dry ethanol was added a slurry of 2.52 parts of triacetylphloroglucinol and ll.0 parts of diethyl oxalate in 50 parts of dry ethanol. The mixture was stirred and heated under reflux for 4 hours.

After cooling, the mixture was poured into a separating funnel containing a mixture of ethyl acetate and dilute hydrochloric acid. The ethyl acetate layer was separated, dried over sodium sulphate and evaporated to leave an oil. This oil was dissolved in 50 parts of ethanol containing 0.5 parts of concentrated hydrochloric acid and the solution was refluxed for 30 minutes. The volume was then reduced to 30 ml. and allowed to cool whence a brown solid crystallised out. This solid was redissolved in aqueous ethanol and treated with sodium bicarbonate. The solution was then heated till thin layer chromatography showed that hydrolysis was complete. The solution was cooled and acidified to give 2,6- ,l0-tricarboxy-4,8,l2-trioxo-4H,8H,lZH-benzo [1,2-b: 3.4-b': 5,6-b"] tripyran hemihydrate as a yellow solid, melting point 275-277C.

Analysis Found: (.5 .2; A

b. 2.6,l-Tricarboxy-4,8,l 2-Trioxo-4H,8H.l2HBenzo [1,2-b: 3,4-b': 5,6-b"] Tripyran Trisodium Salt By the method of Example (d) 0.088 parts of 2,6,- lO-tricarboxy-4,8.l2-tri0xo-4H.8H.l2H-benzo [l,2-b: 3,4-b': 5,6-b"] tripyran hemihydrate was converted into 2.6,l0-tricarboxy-4.8, l 2-trioxo-4H,8H. l 2H-benzo [l.2-b: 3,4-b': 5.6-b"] tripyran trisodium salt.

EXAMPLE l7 2 ,8-Dicarboxy-4,6-Dioxol O-N-Pentyl-4H.6H-Benzo [1,2-b: 5,4-b] Dipyran a. 2,-Diacetoxy-N-Pentylbenzene A solution of 3.7 parts of Z-n-pentylresorcinol, 3.25 parts of acetyl chloride and 3.25 parts of pyridine in 50 parts of chloroform was heated under reflux for 18 hours. The solution was cooled and then pouredinto water.

The chloroform layer was separated and washed with dilute hydrochloric acid, water, sodium hydroxide-solution and water, then dried over sodium sulphate. The chloroform was then evaporated to leave an oil which was distilled to give 2,6-diacetoxy-n-pentylbeniene, boiling point l42-l44C at a pressure of 1.75mms of mercury.

Analysis Found: C. 68.1 H. 7.71%. (T -H 0 requires: C. 68.16; H. 7.63%.

b. 4,6-Diacetyl-2-N-Pentylresorcinol By the method of Example 15 (a) 4.4 parts of 2,6-diacetyl-n-pentylbenzene were converted into 4.6- diacetyl-Z-n-pentylresorcinol. This compound was not completely purified but was used directly for the next stage of the reaction. c. 2,8-Dicarboxy-4,6-Dioxo-l0-N-Pentyl-4H.6H-Benzo [l,2-b: 5,4-b] Dipyran By the method of Example 16 (a) 1.34 parts of crude 4,6-diacetyl-2-n-pentylresorcinol were converted into 2,8-dicarboxy-4.6-dioxo-l O-n-pentyl-4H,6H-benzo [l,2-b: 5 .4-b} dipyran, melting point 268C (d).

Analysis Found: C, 61.] ;H. 4.76%. C H O requires: C. 6i .29; H. 4.33%.

d. 2,8-Dicarboxy-4,6-Dioxo-l0-N-Pentyl-4H.6H- Benzo [l,2b: 5,4-b] Dipyran Disodium Salt By the method of Example 15 (d) 0.046 parts of 2,8- dicarboxy-4,6-dioxo-lO-n-pentyl-4H,6H-benzo [1,2-b: 5,4-b] dipyran were converted into 2,8-dicarboxy-4,6- dioxo-l0-n-pentyl-4H,6H-benzo [1,2-b: 5,4-b'] dipyran disodium salt.

EXAMPLE l8 2,8-Dicarboxy-5Methoxy-4.6-DioxolO-Propyl- 4l-l,6H-Benzo [1,2-b: 5,4-b] Dipyran a. 2,6-Diacetyl-3-Allyloxy-S-Benzyloxyphenol A mixture of 13.5 parts of 2,4-diacetyl-5 allyloxyresoreinol. 7.5 parts of anhydrous potassium carbonate, 13 parts of benzyl chloride. 0.5 parts of potassium iodide, and 60 parts of dry acetone was stirred and refluxed for 43 hours. Most of the acetone was removed. and the residue was mixed with water and acidified to give an orange oil. which was extracted with ether. The ethereal portion was extracted repeatedly with 2N sodium hydroxide solution, which was then acidified to give 2,6-diacetyl-3-allyloxy-5- benzyloxyphenol as pale yellow needles. melting point 92-92.5C.

Analysis Found: C. 70.6; H. 5.84%. H- 0 requires: C. 70.6; H. 5.92%.

Found: C, 71.

2 C H Q, requires: C. 71.2; "A.

c. 4,6-Diacetyl-5Meth0xy-2-Propylresorcinol Under an atmosphere of nitrogen 6.6 parts of 2,6- diacetyl-3-allyloxy-5-benzyloxyanisole and 15 parts of tetralin were refluxed for 4 hours. The mixture was cooled, diluted with light petroleum (b.p. 40-60) and extracted repeatedly with 2N sodium hydroxide. The

combined alkaline extracts were washed with light petroleum, acidified, and extracted with ether, which was then evaporated to give 2.4 parts of a red oil. The oil was taken up in 100 parts of ethanol containing 2 drops of concentrated hydrochloric acid, and hydrogenated at 45 p.s.i. for one hour over 0.5 parts of 5% palladium on charcoal. The mixture was filtered and evaporated to yield 1.7 parts of a red oil, which was repeatedly extracted with hot light petroleum (b.p. 4060). The extracts were evaporated and distilled at l50-l70C/0.6 mm to give a viscous oil, which was crystallised from aqueous ethanol to afford 4,6-diacetyl-5-methoxy-2- propylresorcinol as needles, melting point C.

Analysis Found: c. 63.3: H. 6.6%. C H Q; requires: C, 63.1; H. 6.81%.

Found: C.

5.08%. C H O requires: C. 5.15%.

e. 2.8-Dicarboxy-5-Methoxy-4,6-Dioxo-lO-Propyl- 4H.6H-Benzo [1.2-b: 5,4-b] Dipyran By the method of Example 15 (c) 2.4 parts of 2,8- diethoxycarbonyl-S-methoxy-4,6-dioxo-IO-propyl- 35 4H,6H-benzo [1,2-b: 5,4-b] dipyran were converted into 2.8-dicarboxy-5-methoxy-4,6-dioxo-10-propyl- 4H,6H-benzo [1,2-b: 5,4-b'] dipyran, melting point 278-279C(d).

Analysis Found: C, 57.8: H. 3.74%. C H O requires: C. 57.8; H. 77%.

f. 2,8-Dicarboxy-5-Methoxy-4,6-Dioxo-10-Propyl- 4H,6H-Benzo [1,2-b: 5,4-b'] Dipyran Disodium Salt By the method of Example (d) 0.567 parts of 2,8- dicarboxy-S-methoxy-4,6-dioxo-10-propyl-4H,6H- benzo [1,2-b: 5,4-b] dipyran were converted into 2,8- dicarboxy-S-methoxy-4,6-dioxo-10-propyl-4H,6H- benzo [1,2-b: 5,4-b'] dipyran disodium salt.

EXAMPLE 19 2,8-Dicarboxy-5-Methoxy-4,10-Dioxo-6-Propyl- 4H,]OH-Benzo [1,2-b: 3,4-b] Dipyran a. 2,4-Diacetyl-6-Allyl-5-Methoxyresorcinol A mixture 7 of 15.5 parts of 2,4-diacetyl-5- allyloxyresorcinol, 8.6 parts of anhydrous potassium carbonate. 10 parts of methyl iodide, and 80 parts of acetone was refluxed for 16 hours. Most of the acetone was removed and the residue was diluted with water, acidified, and extracted with ether, which yielded 17 parts of an oil on evaporation. The oil was refluxed with 17 parts of tetralin for 3.5 hours. The mixture was cooled and poured into 2N sodium hydroxide solution. The aqueous layer was washed with benzene, and then extracted repeatedly with ethyl acetate. The combined ethyl acetate portions were evaporated to give a solid, which crystallised from aqueous ethanol to afford 2,4- diacetyl-6-allyl-5-methoxy-resorcino1 as long fibrous needles, melting point 84.5-85C.

Analysis Found: C, 63.9: H. C H Q, requires: C, 63.6;1-1,

b. 2,4-Diacetyl-5-Methoxy-6-Propylresorcinol An ethanolic solution of 1.3 parts of 2,4-diacetyl-6- allyl-S-methoxyresorcinol was hydrogenated at 45 psi. for 2 hours over 0.5 parts of 5% palladium on charcoal. The mixture was filtered and evaporated to give a green oil which crystallised from aqueous ethanol to afford 2,4-diacetyl-5-methoxy--propylresorcinol as long needies, melting point 48-49C.

Analysis Found: C. 62.7; H, 6.85%. C H,,.O,, requires: C, 63.1: H, 6.76%.

Found: C,

61. ;H, 5.08%. C H O requires: C, 61. H, 5.15%.

d. 2,8-Dicarboxy-5-Methoxy-4, l 0-Dioxo-6-Propyl- 4H,lOH-Benzo [1.2-b: 3,4-b] Dipyran Hemihydrate By the method of Example 15 (c) 0.5 parts of 2,8- diethoxycarbonyl-5-methoxy-4,l0-dioxo-6-propyl- 4H,1OH-benzo [1,2-b: 3,4-b'] dipyran were converted into 2,8-dicarboxy-5-methoxy-4, l O-dioxo--propyl- 4H,]0H-benzo [1,2-b: 3,4-b'] dipyran hemihydrate, melting point 268270"C.

Analysis e. 2,8-Dicarboxy-5-Methoxy-4,10-Dioxo-6-Propyl- 4H,l0H-Benzo [1,2-b: 3,4-b] Dipyran Disodium Salt By the method of Example 15 (d) 0.132 parts of 2,8- dicarboxy-5-methoxy-4,10-dioxo-6-propyl-4H,lOH- berizo [1,2-b: 3,4-b'] dipyran hemihydrate were converted into 2,8-dicarboxy-5-methoxy-4,10-dioxo-6- propyl-4H,10H-benzo [1,2-b: 3,4-b] dipyran disodium salt. I

EXAMPLE 20.

' 2,8-Dicarboxy-10-Ethyl-S-Methyl-4,6-Dioxo-4H,6H-

Benzo [1,2-b: 5,4-b'] Dipyran a. 1,3-Bis-(1,Z-Trans-Dicarboxyvinyloxy)-2-Ethyl-5- Methylbenzene A solution of 3 parts of 2-ethyl-5-methylresorcinol and 6.5 parts of dimethyl acetylnedicarboxylate in 10 parts ofdioxan was treated with 3 drops ofa 40% aqueous solution of benzyltrimethyl-ammonium hydroxide and subsequently heated on a steam-bath for 15 minutes. The mixture was then cooled and treated with 30 parts ofa 25% sodium hydroxide solution in water and reheated on a steam-bath for 20 minutes. The mixture was cooled, washed with ether to remove dioxan, acidified with sulfuric acid and extracted with ether. Evaporation of the second ethereal solution left 1,3-bis-(1,2- trans-dicarboxyvinyloxy)-2-ethyl-5-methylbenzene, melting point 162.5C.

Analysis Found: c. 53.0; H, 4.33%. C 7H| O|tl requires: C, 53.65: H, 4.21%.

b. 2,8-Dicarboxy-10-Ethy1-5-Methyl-4,6-Dioxo- 4H,6H-Benzo [1,2-b: 5,4-b] Dipyran Hemihydrate To a stirred solution of 25 parts of chlorosulphonic acid was added, in small lots, 3 parts of 1,3-bis-(1,2- transdicarboxyvinyloxy)-Z-ethyI-S-methylbenzene. The solution was allowed to stand for l0'minutes then it was carefully diluted with 25 parts of concentrated sulphuric acid, then heated briefly at 50C, cooled and finally poured on to 350 parts of ice. A precipitate was deposited which was filtered off and dried to leave a brown powder. The product was boiled with aqueous ethanol, filtered off and dried, then dissolved in sodium bicarbonate solution and reprecipitated with hydrochloric acid, thenagain filtered off and dried to leave 2,8-dicarboxy-10vethyl-5-methyl-4,6-dioxo-4H,6H- benzo [1,2-b: 5,4-b] dipyran hemihydrate, melting point 312C ((1).

Analysis c. 2,8-Dicarboxy-l-Ethyl-5-Methyl-4.6-Dioxo- 4H,6H-Benzo il.2-b: 5.4-b] Dipyran Disodium Salt I By the method of Example l ((1) 0.38 parts of 2,8-dicarboxy-l0-ethyl- 5-methyl-4,6-dioxo-4H,6H- benzo [l,2-b: 5,4-b] dipyran hemihydrate were converted into 2.8-dicarboxyl O-ethyl-5-methyl-4.6-dioxo- 4H,6H-benzo [1,2-b: 5,4-b'] dipyran disodium salt.

Found: C. 60.2; H, 3.78%. C H O requires: C. 60.34; H, 3.9471.

b. 2,7-Dicarboxy-4,9-Dioxo-4H,9H-Benzo [l,2-b: 4.5-

male) having a body weight of from 100 to 150 gms. were infected subcutaneously at weekly intervals with N. muris larvae in doses increasing from about 200 larvae per animal to 2000 larvae per animal in order to establish the infection in rats. After 8 weeks the rats were bled by heart puncture and 15-20 mls. of blood collected from each animal. The blood samples were then centrifuged at 3500 rpm. for 30 minutes in order to remove the blood cells from the blood plasma. The blood was collected and used to provide a serum containing N. muris antibody. A pilot sensitivity test was carried out to determine the least quantity of serum required to give a skin weal in control animals in the test described below of 2 cm diameter. It was found that optimum sensitivity of rats in the body weight range l00-l30 gms was obtained using a serum diluted with eight parts of water. This diluted solution is called antibody serum A.

The antigen to react with the antibody in serum A was prepared by removing N. muris worms from the gut of the infested rats, centrifuging the homogenate and collecting the supernatant liquor. This liquor was diluted with water to give a protein content of l g./ml. and is known as serum B.

bi] Dlpyran Hemhydrate Sprague-Dawley rats in the body weight range 100 to the method of Ex ample 15 (C) parts of 130 gms. were sensitized by intra dermal injection of l w 9 0.1 mls. ofserum A into the right flank. Sensitivity was d'pyran were converted j' f allowed to develop for 24 hours and the rats were then z 1 dlpyran hemlhy' injected intravenously with l ml./l00 gms. body weight draw meltmg pomt 340 ofa mixture of serum B (0.25 mls.), Evans Blue dye so- Analysls lution (0.25 mls.) and the solution of the compound under test (0.5 mls. varying percentages of active mat- Found. C 53 4 H 2 36% ter). Insoluble compounds were administered as a sepa- C,.H,.,0,.. /2H. .O requires: C. 53.0; H. 2 25%. rate intraperitoneal injection 5 minutes before intravenous administration of serum B and Evans Blue dye.

c. 2,7-Dicarboxy-4,9-Dioxo-4H,9H-Benzo [l,2-b: 4,5- For each percentage level of active matter in the solub] Dipyran Disodium Salt tion under test five rats were injected. Five rats were By the method of Example 15 (d) 0.154 parts of2,7- used as controls in each test. The dosages of the comdicarboxy-4.9-dioxo-4H,9H-benzo [1,2-b: 4,5-b] dipypound under test were selected so as to give a range of ran hemihydrate were converted into 2,7-dicarboxy- 40 inhibition values. 4,9-dioxo-4H,9H-benzo [1,2-b: 4,5-b] dipyran diso- Thirty minutes after injection of serum B the rats dium salt. were killed and the skins removed and reversed. The

intensit of the ana hylactic reaction was assessed by EXAMPLE 22 comparing the size 3f the characteristic blue weal pro- The Compounds descr bed in Table I e e tested I0 duced by spread of the Evans Blue dye from the sensitiassess their acute toxicity and their effectiveness in insaiion ite, with the size of the weal in the control anihibiting antibody-antigen reactions. mals. The size of the weal was rated as 0 (no weal de- In most cases the compounds of the invention were tected, i.e. 100% inhibition) to 4 (no difference in size found to possess very low toxicity values, that is they f weal, i.e. no inhibition) and the percentage inhibihad LD values of at least 1,000 mg/Kg of the comti f h d s l vel c lculated as;- pound (expressed in terms of the free acid).

In the antibody-antigen tests, the effectiveness of the mhlbmon (Control group Score treated group compounds of the invention in inhibiting the passive score) X loo/Control group score cutaneous anaphylaxis in rats was assessed. It has been Th p rcentage i hibitions for the various dose levels proved that this form of test gives reliable qualitative were plotted graphically for each compound. From indications of the ability of the compounds under test these graphs the dosage required to achieve a 50% inhito inhibit antibody-antigen reactions in man. bition ofthe anaphylactic reaction (lD may be deter- In this test method Sprague-Dawley rats (male or femined. These results are tabulated in Table II.

TAB LEO ID, values in Name of Compound LD mg/Kg I mg/Kg of the salt 4,l0-dioxo-2,8-dicarboxy-5-methoxy-4H.lOH-benzo (l,2-b:3,4-b) dipyran disodium salt I000 0.73

4,6-dioxo-2,8-dicarboxy-4H.6H-benzo (1,2-b: 5.4-b') dipyran disodium salt I000 0J8 4,l0-dioxo-2.8-dicarboxy-4H,lOH-benzo (l,2-b:3,4-b') dipyran disodium salt 1000 7.6

4.l0-dioxo-2.8-dicarboxy-5-benzyloxy-4H.IOH-benzo (l.2-b:3,4-b) dipyran'disodium salt 500. 0.36

4,l0-dioxo-2,8-dicarb'oxy-5methyl-4H.lOH-benzo l,2-b:3.4-b) dipyran disodium salt circa 1000 9.5

4,6-dioxo-2.8-dicarboxy-5-methoxy-4H,6H-benzo (l,2-b:5,4-b') dipyran disodium salt 0.32 

1. A PHARMACEUTICAL COMPOSITION FOR THE PREVENTION OF THE SYMPTOMS OF ASTHMA COMPRISING AN EFFECTIVE AMOUNT FOR THE PROPHYLACTIC TREATMENT OF ASTHMA OF A COMPOUND OF FORMULA,
 2. A composition according to claim 1, wherein those of P, Q, R and T not forming a -CO-CR1 C(COOH)-O- chain are hydrogen or halogen, hydroxy, nitro, lower alkyl, lower alkenyl, benzyl, phenyl, lower alkoxy, lower alkenyloxy, phenyl, benzyloxy or the fused ring substituents specified in Claim 1 or such groups carrying a halogen, hydroxy or lower alkoxy substituent.
 3. A composition according to claim 1, wherein those of P, Q, R and T not forming a -CO-CR1 C(COOH)-O- chain are hydrogen, chlorine, bromine, nitro or lower alkyl or alkoxy group containing from 1 to 6 carbon atoms which may carry a hydroxy, lower alkoxy or phenyl substituent.
 4. A composition according to claim 1 comprising a compound of formula
 5. A composition according to claim 1 in which those of P, Q, R and T which do not form a chain -COCR1 C(COOH)-O- are selected from the group consisting of hydrogen, hydroxy, nitro, halogen, lower alkyl, lower alkoxy or lower alkenyloxy groups (which groups may carry a hydroxy or lower alkoxy substituent), a benzyl group or an adjacent pair of P, Q, R and T may form a chain -O(CH2)2- and each R1 is selected from the group consisting of hydrogen, alkyl containing from 1 to 10 carbon atoms, alkoxy containing from 1 to 10 carbon atoms and phenyl.
 6. A composition according to claim 1 in which R1 is hydrogen and those of P, Q, R and T which do not form a -COCR1 (COOH)-O-chain are selected from methoxy, hydroxy, nitro, methyl, bromo, benzyloxy, ethyl, chloro, allyloxy, butyl, propyl and pentyl.
 7. A composition according to claim 1, wherein the compound of formula I is 4, 10-Dioxo-5-methoxy-2,8-dicarboxy-4H,10H-benzo (1, 2-b:-3,4-b'')dipyran.
 8. A composition according to claim 1 in a form suitable for administration by inhalation.
 9. A composition according to claim 8 further containing a bronchodilator.
 10. A composition according to claim 9 wherein the bronchodilator is isoprenaline, adrenaline, orciprenaline, isoetharine or a pharmaceutically acceptable salt of any one thereof.
 11. A method of preventing the symptoms of the asthmatic condition involving an antigen-antibody reaction which comprises administering to a patient in need thereof an effective amount for the prophylactic treatment of asthma of a compound of formula I,
 12. A method according to claim 11, wherein the compound administered is 4,10-dioxo-5-methoxy-2,8-dicarboxy-4H,10H-benzo(1,2-b:3,4-b'') dipyran or a sodium salt thereof. 